Variable displacement positive displacement pump

ABSTRACT

In an axial, variable displacement, positive displacement pump having a swash plate mounted on a drive shaft for rotation therewith and a non-rotatable wobble plate surrounding the swash plate but isolated there from through bearings includes a slide mechanism disposed on the shaft that can be axially displaced along the shaft as the shaft is being driven to thereby vary the angle of inclination of the swash plate and wobble plate relative to the drive shaft. The pump further includes a unitary in-line valve assembly including suction and discharge poppet valves for each cylinder whereby the overall diameter of the cylinder block can be minimized.

BACKGROUND OF THE INVENTION

[0001] I. Field of the Invention

[0002] This invention relates generally to fluid handling pumps, and more particularly to an improved, multi-cylinder, variable displacement, positive-displacement pump that permits adjustment of the plunger's stroke while the pump is being driven to thereby vary the flow rate of the fluid being pumped.

[0003] II. Discussion of the Prior Art

[0004] In conventional positive displacement piston or plunger pumps of the in-line type, a plurality of pistons/plungers are disposed in parallel aligned bores in the pump's cylinder block and are reciprocally driven, via a crank shaft, by means of connecting rods that convert rotary motion of the crank to reciprocating motion of the pistons/plungers. Typical of this prior art arrangement is the Triplex pump described in the Uchiyam U.S. Pat. No. 3,558,244.

[0005] In the hydraulic power industry, there are variable displacement, positive-displacement pumps that use a non-rotating swash plate whose angle is adjustable. In such pumps, the cylinder barrel rotates and the pistons rotate with the barrel and one end thereof rides on the tilted swash plate to thereby impart reciprocating motion to the pistons. Because the hydraulic fluid being pumped is very clean and lubricious, it is possible to provide porting to the cylinders as the top of the barrel rotates across appropriate suction and discharge ports. Thus, from an application point of view, such a design can only be used when pumping clean, lubricating fluids, such as, hydraulic oil.

[0006] By keeping the cylinders stationary and rotating the swash plate, check valves can be used which allows for the pumping of non-lubricating and dirty fluids. One type of axial piston/plunger pump that is designed to pump non-lubricating fluids, typically has a fixed cylinder block and a rotating swash plate that coacts with the pistons to impart reciprocating action due to the inclination of the rotating swash plate relative to the drive shaft used to rotate the swash plate. Many refrigeration unit compressors use a rotating swash plate to impart reciprocatory displacement of plural pistons. In this regard, reference is made to the Kato et al. U.S. Pat. No. 6,241,483. In this design, the angle of inclination of the swash plate is controlled as a function of the pressure in the pump's crank housing.

[0007] In any such design, due consideration must be given to the joint coupling the piston/plunger to the swash plate. The joint necessarily must compensate for a linear motion and a progressing angular motion as the tilted swash plate rotates through 360°.

[0008] On some inexpensive swash plate driven positive displacement piston/plunger pumps, a return spring is provided on the piston's connecting rod to force a smoothly rounded end of the connecting rod against the surface of the swash plate. There are several significant drawbacks to this design. Firstly, the spring pressure is present in both the suction and discharge stroke of the piston/plunger and thus adds to the force in the discharge stroke. Secondly, the interface between the connecting rods and the swash plate must tolerate the rotational velocity and the orbital motion as it is forced against the swash plate by the return spring. This results in a very high PV (pressure, velocity) wear rate of the swash plate and the mating end of the connecting rod. Thirdly, the return spring is limited to the speed at which the pump is made to operate, based on the spring mass relationship for a first critical frequency. If the pump is made to run too fast or the return spring loses its resiliency over time, then the pistons/plungers will, for part of the travel, lose contact with the swash plate, causing rapid destruction of the pump. In addition, the spring will fatigue over time and will eventually fail.

[0009] Another method of translating the wobble plate rotation to reciprocating movement of the pistons/plungers is also used in the compressor industry. For example, as shown in the Kimura et al U.S. Pat. No. 5,336,056, an inner, convex spherical shoe disposed about one end of a connecting rod cooperates with a mating concave outer shoe having a spherical contour and which is fitted into a C-form joint designed into a lower end of the piston/plunger. While this method of interfacing the wobble plate with the piston/plunger offers significant advantage over the use of the return spring approach described above, it still has inherent disadvantages. Once such disadvantage resides in the fact that the base of the piston assembly must have the C-form recess which necessarily increases the mass of the reciprocating piston/plunger assembly and the loads. It is also necessary to precisely align the piston so that the C-form slot formed in it does not slowly rotate and eventually strike the swash plate. Moreover, the C-form must protrude to the outside of the diameter of the engagement circle with the connecting rod, thus increasing the overall diameter of the pump or compressor.

[0010] Also contributing to an excessive size of a swash plate driven multi-piston, positive displacement pump is the valve arrangement commonly used in such pumps. Referring to FIG. 7 of the drawings, there is schematically shown a conventional valve arrangement used in prior art pumps. For each of the cylinders represented by circles 300, two identical check valves 302 and 304 are required. The suction valves 302 open during the suction stroke of their respective plungers, to allow the fluid being pumped to be drawn into the plunger bores as the plungers leave its top dead center position. During the discharge stroke, the suction check valves 302 close and the discharge valve 304 opens allowing the pressurized fluid to flow through the discharge manifold and out the pump's discharge port.

[0011] While there is an advantage in the prior art design represented by FIG. 7, there are also disadvantages in terms of pump hydraulics. Those skilled in the art recognize that the suction valve becomes restrictive to flow into the cylinder bores during the piston's suction stroke when the fluid flow path into the cylinder head is not direct. To compensate, such pumps must be run at reduced speeds or they may require inlets with additional suction pressure through the use of charge pumps often found in closed-loop hydraulic systems.

[0012] It is also well known that, for axial piston pump designs, a more efficient use of the enclosed volume of the pump is obtained with a greater number of cylinders. Typically five to eleven cylinders may be provided for in a cylinder block. It is also known that utilizing an odd number of cylinders provides a discharge flow with minimal pulsation due to the cancellation of over-lapping cylinder output. As shown in the drawing of FIG. 7, on an axial piston/plunger pump, the cylinders 300 are arranged symmetrically about the central axis 306. In order to feed the cylinders, the manifold is divided into a suction region 308 and a discharge region 310. The conventional valve arrangement illustrated shows that there is only limited room for the valves 302 and 304. Because of the geometry, the valve area to piston area is limited, causing high fluid velocities on both the suction and discharge phases. These high velocities translate into poor suction characteristics and pump inefficiencies. The simple rubber flapper valves found on inexpensive axial diaphragm pumps are not suitable for the higher pressures handled by check valves and, also, they are not as durable. Such flapper valves are limited to applications where low viscosity fluids are being pumped at modest pressures.

[0013] In certain metering applications where a positive displacement pump is to be used to dispense measured quantities of a product, it is desirable that provision be made for varying the pump's displacement and that it be possible to make a displacement adjustment while the pump is running. The most common approach for varying the output of a positive displacement pump is to vary the speed at which the pump is driven. In positive displacement pumps in which a wobble plate is used to impart reciprocatory motion to the pump's plural plungers, it is also known that the displacement can be varied by adjusting the angle of inclination of the swash plate relative to the drive shaft on which it is mounted. In the compressor technology, this angular adjustment is accomplished by controlling the pressure within the crankcase using a needle valve. While this approach is workable for gaseous fluids, it is wholly ineffective when an incompressible liquid is the medium being pumped.

[0014] It is accordingly a principal object of the present invention to provide an improved variable displacement, positive displacement fluid handling pump offering a reduced size because of an improved valving design, a longer life due to an improved coupling of the pump's pistons/plungers to a non-rotating wobble plate, an ability to vary the pump's displacement while the pump is running. Other features and advantages of the invention will also become apparent to those skilled in the art from a study of the specification and drawings hereof.

SUMMARY OF THE INVENTION

[0015] The foregoing features, objects and advantages are achieved in accordance with the present invention by providing a variable displacement, positive displacement pump having a housing to which a cylinder block is attached where the cylinder block has a plurality of bores that are equally radially and circumferentially spaced from a central, longitudinal axis of the cylinder block. A piston/plunger member having first and second ends is disposed in each of the plurality of bores. The pump's drive shaft is journaled for rotation in the housing member along an axis that is aligned with the central axis of the cylinder block. A swash plate is affixed to and rotatable with the drive shaft within the housing member. A non-rotatable wobble plate assembly with a central bore formed therethrough and with an annular bearing disposed in the bore is in concentric, surrounding relation to the swash plate. The pistons/plungers are joined to the non-rotatable wobble plate, using spherical ball joint members that couple a ball on the first end of each of the piston/plunger members to sockets on the wobble plate created by spherical thrust washers. A suction manifold is affixed to the cylinder block and, in turn, a discharge manifold is bolted to the suction manifold. The suction manifold includes an inlet port and the discharge manifold includes a discharge port. Unitary, replaceable in-line, valve cartridges for each of the piston/plunger members are disposed in the discharge manifold. Each valve assembly comprises a suction poppet and a discharge poppet that are disposed in longitudinal alignment with a central axis of its associated piston/plunger. The two poppets are arranged such that the discharge poppet closes to isolate the discharge manifold from the suction manifold during a suction stroke of the plunger member while the suction poppet opens to allow fluid to flow from the suction manifold into a changing volume of the cylinder bore as the plunger member rotates. The discharge poppet opens while the suction poppet closes as the plunger moves in a direction toward the cylinder head.

[0016] To vary the displacement of the pistons/plungers within their respective bores, a slide mechanism is provided on the drive shaft and pinned linkages are used to join the slide member to the swash plate. The slide can be displaced from outside of the housing with the pump running.

[0017] There are, of course, additional features of the invention that will be described hereinafter, which will form the subject matter of the appended claims. Those skilled in the art will appreciate that the preferred embodiments may readily be used as a basis for designing other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions since they do not depart from the spirit and scope of the present invention. The foregoing and other features and other advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like numerals in the several views refer to corresponding parts.

DESCRIPTION OF TILE DRAWINGS

[0018]FIG. 1 is a partially sectioned perspective view of the variable positive displacement pump of the present invention;

[0019]FIG. 2 is a right end view of the variable positive displacement pump of the FIG. 1 showing where the sectional views of FIGS. 4 and 5 are taken;

[0020]FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 4;

[0021]FIG. 4 is a cross-sectional view taken along the line 4-4 in FIG. 2;

[0022]FIG. 5 is a cross-sectional view taken along the line 5-5 in FIG. 2;

[0023]FIG. 6 is a partial, longitudinal, cross-section, detailed view showing the manifold and piston assembly of the variable positive displacement pump;

[0024]FIG. 7 is a schematic representation of a prior art pump having a conventional valving arrangement;

[0025]FIG. 8 is a schematic diagram of the oil lubrication features of the pump; and

[0026]FIG. 9 is a detailed cross-section view of the anti-rotation assembly illustrating the oil distribution features thereof

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the device and associated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import.

[0028] Referring initially to FIG. 1, there is indicated generally by numeral 10 a perspective view of a variable positive displacement pump constructed in accordance with the present invention. While the preferred embodiment to be described is a piston or plunger pump, it is to be understood that the inventive principles may also be applied to other positive displacement pumps, e.g., diaphragm pumps, as well.

[0029] The pump may be considered as including a wet end 12 and an oil lubricated end 14. The wet end includes a cylinder block 16 a suction manifold 17 having an inlet or suction port 18 and bolted thereto is a discharge manifold 20. A discharge port 21 is located on the discharge manifold 20.

[0030] The oil end 14 of the pump includes a lubrication housing 22 having an integrally formed base 24 that is adapted to be bolted to a support frame (not shown). Journaled within the housing is a drive shaft 26. It is journaled for rotation in suitable bearings and the drive shaft has a swash plate 28 affixed to and rotatable with the shaft 26. Also visible in the view of FIG. 1 is a wobble plate assembly 30, which surrounds the rotatable swash plate and which is free to nutate, but is precluded from rotating, by an anti-rotation device, indicated generally by numeral 32. The nutating motion of the wobble plate assembly 30 imparts reciprocal, rectilinear movement to a plurality of pistons contained within bores in the cylinder block 16. The pump design depicted in the drawings accommodates five pistons, but a greater or a fewer number can be used.

[0031] The piston stroke, and therefore, the displacement of the pump cylinders is adjustable by altering the angle at which the swash plate 28 and the surrounding wobble plate 30 are oriented relative to the drive shaft 26. When the wobble plate is perpendicular to the drive shaft, the pump is in its “no flow” state. In the variable, positive-displacement pump of the present invention, the stroke adjustment can be made with the pump running. The adjustment may be made manually with a crank or knob or can be electronically controlled using a stepper or servo motor, as at 36, each of which is arranged to drive a worm gear assembly 38 that is coupled to a pair of actuating screws 40. The actuating screws each have a traveling nut 42 that is coupled, via a control yoke as at 43 and through linkages 44 to the swash plate 28. Displacement of the traveling nut along the length of the actuating screws thus adjusts the tilt angle of the swash plate 28 and the wobble plate 30.

[0032] Referring to the sectioned end view of FIG. 3, the worm gear assembly 38 includes a control shaft 46, which, as mentioned, is adapted to be manually or automatically rotated by a crank knob attached to one end of control shaft 46 or a suitable electric motor coupled to the opposite end. Worms 48 and 50 on the control shaft mate with worm gears 52 and 54 that are affixed to the outer ends of actuating screws 56 and 58, respectively.

[0033] Turning now to the cross-sectional views of FIGS. 4 and 5, it will be seen that the drive shaft 26 is journaled for rotation in a bore 60 forming a part of the cylinder block 16. More particularly, the bores 60 contain a tapered roller bearing set 62 for journaling the shaft 26. The rearward end of the drive shaft 26 is also journaled for rotation by means of roller bearings 68 located within a cavity 70 at the rear end 72 of the pump body or housing 22.

[0034] As seen in FIG. 1, the central portion 27 of the drive shaft 26 may be of a hex-shaped cross-section or may be cylindrical but which has flats machined on diametrically opposed sides of the drive shaft. Fitted onto the drive shaft so as to subtend the flat surfaces is the swash plate 28. As seen in the cross-sectional view of FIG. 4, because of the flats, the swash plate can be tipped to have its angle with the shaft adjusted. The swash plate has a tapered central bore 74. A pin 76 passes through aligned holes in the swash plate and the shaft 26, which allows the swash plate 28 to rotate with the drive shaft 26 and to be tipped at a desired angle (within predetermined limits) with respect to the centerline of the shaft due to the taper of the bore 74. Fitted onto a hub portion 78 of the rotating swash plate 28 in surrounding rotation is a set of double-row ball bearings 80 (FIG. 5).

[0035] Referring still to FIG. 4, the wobble plate assembly 30 comprises an outer thrust support plate 82, a rear annular thrust plate 84 and a second or outer thrust plate 86 that sandwich an annular wobble plate 88 surrounding the bearings 80. This assembly is held together by socket head cap screws 85 passing through the assembly and into threaded bores, as at 90 (FIG. 1).

[0036] An important feature of the present pump design is the manner in which plural pistons or plungers are coupled to the wobble plate so that reciprocating movement of the piston takes place as the wobble plate assembly 30 nutates when the drive shaft 26 is rotated. The cross-sectional view of FIG. 4 shows one of a plurality of plungers driven by the wobble plate assembly. It is identified by numeral 92. In this figure, the plunger 92 is shown as being at the bottom of its stroke. The remaining pistons (not shown) are intermediate top dead center and bottom dead center. A ball joint assembly 94 includes a spherical ball member 96 formed on the end of a threaded connecting rod shaft 98 that fits into an internally threaded bore 100 formed in the bottom end of the piston/plunger 92. The shaft 98 passes through an aperture in the thrust plate 86 and the ball member 96 is captured between spherical thrust washers 102 and 104 that are disposed between the annular thrust plates 84 and 86. Provision is made for an oil lubricant in the housing to reach the mating surfaces of the ball joint with the thrust washers by way of a port formed through the spherical thrust washer 102 leading to the interface of the thrust washer with the ball 96.

[0037] As seen in FIG. 5, the actuating screw members 40 and 41 are journaled for rotation in the housing 22. More particularly, and with reference to the actuating screw 41, it has its rearward end 105 disposed in a bronze sleeve bearing 106 that is fitted into a removable end cap 108 bolted to the housing 22. Its other end is journaled in a set of roller bearings 110 disposed in a bearing cup 112 that forms a part of the housing. The actuating screw 40 is mounted in an identical manner such that each is free to rotate about a longitudinal axis that is parallel to and latterly offset from the axis of the drive shaft 26. Cooperating with external threads on the actuating screw shafts 40 and 41 are internally threaded travelers 114 that are affixed to a control yoke member 43. The control yoke member 43 cooperates with a control slide 118 that rotates with the shaft 26, but which is isolated from the control yoke 43 by a double row ball bearing set 120. The control yoke 43 is coupled to the rotating swash plate 78 by first and second linkage bars 44 which are joined to the control slide 118 and the rotating swash plate 28 by linkage pins 126 and 128, respectively.

[0038] From what has been thus far described, as the drive shaft 26 is being driven at a set speed by a pump motor (not shown), the control shaft 46 can be rotated manually or automatically to rotate the worm gears 52 and 54, which, in turn, cause longitudinal translation of the control slide 118 to vary the tilt of the swash plate assembly 28 as well as the wobble plate 30 via linkage bars 44. This, in turn, varies the stroke of the piston 92 and the pump's displacement.

[0039] With reference to FIGS. 1 and 4, to prevent the wobble plate from rotating with the swash plate 28, an anti-rotation assembly 32 is provided. It includes a rocker shaft 132 that is journaled for rotation within a bearing cap 134 on a housing cover plate 136 by bearings 138. Affixed to the rocker shaft 132 is a rocker member 140 having an arcuate groove 142 formed therein. Fitted into the groove 142 is a vane member 144 that projects radially from the wobble plate assembly. As the wobble plate nutates through its range of motion, the rocker member 140 pivots back and forth about its shaft 132 while preventing rotary motion of the wobble plate.

[0040] The pump's cylinder block 16 includes a plurality of cylinder bores (here numbering five) that are equally circumferentially and radially spaced relative to the longitudinal axis of the pump with which the drive shaft 26 is centered. Specifically, the cylinder block 16 includes a base plate 150 that bolts to the pump body 11 containing the pump's lubricating oil. The plate 150 has a cylindrical bore, as at 151 in FIG. 3, for each of the pistons/plungers utilized in the pump. Likewise, the suction manifold 17 has a base 152 that also has circumferentially and radially spaced bores formed therethrough which are aligned with the bores in the base plate 150 of the cylinder block 16.

[0041]FIG. 4 and the enlarged detailed view of FIG. 6 illustrate one of the pistons/plungers 92, along with the seal arrangement that is disposed between the piston/plunger 92 and the base plates 150 and 152 of the cylinder block 16 and suction manifold 17, respectively. The plunger rod 92 includes a cylindrical stem portion of a first diameter into which the threaded connecting rod shaft 98 attaches. This stem portion is necked down to a reduced diameter segment 93 and concentrically surrounding the reduced diameter portion 93 is a tubular ceramic plunger 95. An acorn nut 97 holds the tubular plunger 95 in place. When a pump of the type described herein is to be used to pump corrosive or abrasive fluids, the ceramic plunger 95 proves very suitable in terms of its resistance to wear an erosion. It may readily be removed for replacement, however, without the need to uncouple the piston/plunger from the wobble plate.

[0042] Fitted between base or stem portion of the plunger rod 92 and the cylindrical wall of the cylinder block 16 is a sleeve bearing 99 and a stainless steel oil seal retainer 101, a rod seal 103 and a rod wiper seal 105. This seal arrangement inhibits passage of lubricating oil along the plunger stem.

[0043] With continued reference to FIG. 6, it can be seen that a seal cartridge housing 154 is positioned in surrounding relationship to the ceramic plunger 95 and located between it and the outside diameter of the plunger 95 is a lantern ring 156, providing support to a high pressure, elastomeric U-cup seal 158. The lantern ring supports a graphite guide bushing 160 and provides lubrication to the guide bushing from the pumped fluid from the suction side of the pump. Sealing the suction side of the pump from the atmosphere is another low-pressure cup seal 162. It is made of an elastomeric material is held in place by a low-pressure seal retainer 164 and is exposed to atmospheric pressure through a weep hole formed in the cylinder block 16. The seal arrangement just described is held in place by a seal cartridge retainer 166 having external threads for mating with the internal threads formed on the seal cartridge housing. The lantern ring 156 not only supports the high pressure elastomeric cup seal 158, but also provides a path for fluid being pumped to lubricate and cool the plunger journal bearing, the low pressure seal 162 and the O-ring seals 168 and 170. The plunger journal bearing is preferably made of graphite or other bearing material compatible with the fluid being pumped while providing the plunger with linear bearing support.

[0044] The seal arrangement just described effectively precludes the liquid being pumped from contaminating the oil lubricant contained within the housing 22. A weep hole 172 (FIG. 4) is formed through the wall of the housing so that any liquid that is not blocked by the aforementioned seal arrangement exits through the weep hole and therefore does not find its way down along the surface of the piston/plunger into the lubrication housing. Moreover, the annular bushing 151 is disposed in the cylinder bore to allow the lubricant contained in the housing to lubricate the surface of the piston while oil seal assembly 101 inhibits exit of oil out weep hole 172.

[0045] Rather than providing separate suction and discharge check valves for each pump cylinder, in the design of the present invention, each cylinder has a compound unitary suction/discharge valve is incorporated into a replaceable cartridge assembly along with the wet end seal elements. These coaxially disposed cartridge elements provide two unique and novel advantages to the pump design. The first is to provide ease of maintenance by allowing each seal element to be serviced independently, without disassembling the entire pump. The second advantage to the arrangement allows for a much smaller pump head diameter. To gain access to the valve cartridges, one need only remove the bolts, as at 174, that holds cover plates, as at 176, to the discharge manifold.

[0046] With continued reference to the assembly drawing of FIG. 1 and the enlarged view of FIG. 6, the in-line suction and discharge valve assembly is indicated generally by numeral 180. It comprises a suction poppet member 182, which is urged by spring 184 into sealing relation with respect to a valve body member 186 having an annular port 188 formed through it. The port 188 is in fluid communication with the suction manifold 17. A discharge poppet valve 190 is urged by a coil spring 192 into sealing relation with respect to a valve seat member 194 that has a port formed through it. Both the suction poppet 182 and the discharge poppet 190 are seated when the piston 92 is at the bottom of its stroke as illustrated in FIG. 4. At this time, the volume of the cylinder not occupied by the piston is filled with the liquid being pumped. As the drive shaft rotates, the nutating plate assembly forces the piston to the right when viewed in FIG. 4, increasing the pressure acting on the suction poppet valve 182 to force it to close. The increased pressure acting on the face of discharge poppet 190 also forces it to open against the bias afforded by the spring 192 causing the charge of liquid being displaced by the piston to flow out through the discharge port 21 (FIG. 1). When the piston reaches its top dead center position, the force of the coil springs 184 and 192 overcome the fluid pressure acting on the respective poppets 182 and 190, again forcing those poppets closed. With continued rotation of the drive shaft, the piston 92 is drawn back from its top dead center position reducing the hydraulic pressure acting against the discharge valve 190 and causing it to seat against the valve seat member 194. The liquid entering the suction port 18 into the suction chamber acts against the suction valve poppet 182 forcing it away from the annular port and allowing flow into the cylinder bore ahead of the free end of the piston 92. The liquid continues to fill this volume until the piston reaches the bottom of its stroke and the cycle then repeats.

[0047] A variable positive displacement pump cannot be allowed to run against a shut or blocked discharge. This could cause the pump to experience a significant pressure spike that could result in damage to the pump. By providing a pressure feedback signal to the servo motor 36 (FIG. 1) that is coupled to the control shaft of the worm gear assembly, the wobble plate can be repositioned to provide a reduced flow “no-flow” condition, thus protecting the pump from damage due to over pressure conditions. Should such pressure transients or “spikes” occur more rapidly than the feedback mechanism of the pump can respond to, a safety valve arrangement is also incorporated into the present invention which allows for brief internal relief of pressure, thus providing the necessary time for the control mechanism to respond in tilting the nutating plate to a reduced or “no-flow” condition.

[0048] With reference to FIG. 4, it will be seen that a safety valve, indicated generally by numeral 200 is centrally disposed in the valve plate 202 and it includes a piston 204 that is held seated against the valve plate by a compression spring 206. Should the pressure in the discharge chamber 208 become excessive, the piston 204 will be exposed to that pressure through port 210 and will move in a direction to compress the spring 206, unseating the piston 204 and allowing the liquid in the discharge chamber to flow through a port 210 back into the low pressure suction chamber. As the pressure in the discharge chamber 208 drops, the spring 206 will again urge the piston 204 back into its seated condition, again blocking the port 210.

[0049] The variable displacement positive displacement pump of the present invention is provided with an oil-end lubrication system illustrated schematically in FIG. 8. As represented there, oil is taken from the pump's oil sump in pump body 22 through a strainer (not shown) and then pumped by an internal oil pump 209 through an oil filter 211 and distributed directly to the linear oil journal bearings 151 for each cylinder and to the unique oil mist lubrication system that is shown in greater detail in FIG. 9. As illustrated in FIG. 9, the anti-rotation assembly 32 is used to uniformly distribute an oil spray to the pump components. Advantage is taken of the back-and-forth twisting action of the rocker assembly 140. Oil is injected into the anti-rotation assembly 32, via a port 137, and travels to the rocker bearing 138 and the spray nozzles 139 through the hollow shaft 141. The spray nozzles then distribute the oil mist, aided by the back-and-forth twisting action of the rocker member 142.

[0050] It can be seen, then, that there is provided by this invention a variable positive displacement pump capable of providing a precise metered flow of fluid that is being run at a constant speed by appropriately adjusting the displacement of the pump's cylinders while the pump is running. Because of the design, it effectively isolates the wet end of the pump from the crankcase where all parts requiring lubrication are bathed in oil. As such, the pump of the present invention may be used to pump non-lubricious and corrosive fluids. 

1. A variable displacement positive displacement pump comprising: (a) a housing member; (b) a cylinder block having a plurality of bores equally radially and circumferentially spaced from a central axis of said cylinder block, said cylinder block being affixed to the housing; (c) a plunger member having first and second ends disposed in each of said plurality of bores; (d) a drive shaft journaled for rotation in the housing member along an axis aligned with the central axis of the cylinder block; (e) a swash plate pivotally affixed to the drive shaft and rotatable therewith; (f) a non-rotatable wobble plate assembly having a central bore formed therethrough, with an annular bearing disposed in the bore of the wobble plate in surrounding relation to the swash plate; (g) spherical ball-joint members coupling the first end of each of said plunger members to the wobble plate for imparting reciprocating axial displacement to the plunger members when the drive shaft is rotated; (h) a cylinder head member affixed to the cylinder block defining a suction manifold and a discharge manifold, the suction manifold including an inlet port and the discharge manifold having a discharge port; and (i) a unitary in-line valve assembly for each of the plunger members disposed in the cylinder head wherein the valve assembly comprises a suction poppet and a discharge poppet disposed in alignment with a central axis of its associated plunger and are arranged such that the discharge poppet closes to isolate the discharge manifold from the suction manifold during a suction stroke of the plunger member while the suction poppet opens to allow fluid to flow from the suction manifold into a changing volume of the cylinder bore as the plunger member moves in a direction away from the cylinder head and the discharge poppet opens while the suction poppet closes as the plunger moves in a direction toward the cylinder head.
 2. The variable displacement positive displacement pump as in claim 1 and further including a means for adjusting a tilt angle of the non-rotatable wobble plate with respect to the axis of the drive shaft.
 3. The variable displacement positive displacement pump as in claim 2 wherein said means for adjusting the tilt angle can be operated as the drive shaft is being driven.
 4. The variable displacement positive displacement pump as in claim 1 and further including a slide mechanism disposed on the drive shaft to be slidable therealong and rotatable therewith, the slide mechanism being linked to the swash plate for incrementally adjusting a tilt angle between the non-rotatable wobble plate and the axis of the drive shaft.
 5. The variable displacement positive displacement pump as in claim 4 and further including at least one lead screw operatively coupled between the housing and the slide mechanism and a worm gear for rotating the lead screw.
 6. The variable displacement positive displacement pump as in claim 5 wherein the worm gear is driven by a worm shaft, said worm shaft being either manually or automatically rotated.
 7. The variable displacement positive displacement pump as in claim 4 and further including a pair of lead screws operatively coupled between the housing and the slide mechanism and a pair of worm gears for driving the pair of lead screws.
 8. The variable displacement positive displacement pump as in claim 7 and further including a worm shaft having a pair of worms thereon for engaging the pair of worm gears and means for driving the worm shaft.
 9. The variable displacement positive displacement pump as in claim 8 wherein the means for driving the worm shaft is a manually operable crank.
 10. The variable displacement positive displacement pump as in claim 8 wherein the means for driving the worm shaft is a servo motor.
 11. The variable displacement positive displacement pump as in claim 7 wherein the slide mechanism comprises a slide on said drive shaft, a control yoke, and a set of bearings disposed between the slide and the control yoke, said control yoke carrying a pair of ball nuts that are in threaded engagement with the pair of lead screws.
 12. The variable displacement positive displacement pump as in claim 1 and further including an anti-rotation assembly operatively disposed between the housing and the wobble plate assembly for preventing rotation of the wobble plate with the swash plate.
 13. The variable displacement positive displacement pump as in claim 12 wherein the anti-rotation assembly comprises a rocker plate member having an arcuate groove formed therein, the rocker plate member having a centrally disposed rocker shaft projecting outwardly therefrom and journaled for pivoting reciprocal rotation relative to the housing, and the wobble plate including a radially extending blade positioned in the arcuate groove of the rocker plate member.
 14. The variable displacement positive displacement pump as in claim 7 wherein the slide mechanism comprises a slide on said drive shaft, a control yoke, and a set of bearings disposed between the slide and the control yoke, said control yoke carrying a pair of ball nuts that are in threaded engagement with the pair of lead screws.
 15. The variable displacement positive displacement pump as in claim 14 wherein said plunger members extend into the housing and a sealing member is disposed in the housing in surrounding relation to the plunger members for inhibiting seepage of the lubricant from the housing.
 16. The variable displacement positive displacement pump as in claim 1 wherein the plurality of bores in the cylinder block each include a seal assembly for cooperating with the plungers to inhibit seepage of the fluid being pumped from the cylinder block.
 17. The variable displacement positive displacement pump as in claim 1 and further including a valve plate located between the cylinder block and the cylinder head, the valve plate including a bore in alignment with each of the bores in the cylinder block with the bores in the valve plate individually containing one of said in-line valve assemblies.
 18. The variable displacement positive displacement pump as in claim 17 wherein the valve plate includes a further bore generally aligned with the central axis of the drive shaft, said further bore containing a spring biased safety poppet normally preventing fluid flow from the discharge manifold to the suction manifold so long as the pressure in the discharge manifold is below a predetermined value.
 19. The variable displacement positive displacement pump as in claim 1 wherein the spherical ball joint members include a stem disposed in a bore formed in the first end of the plunger members, the stem having a sphere formed on a portion of the stem extending out from the bore in the first end of the plunger members; and first and second spherical thrust bearings disposed in surrounding relation to said sphere, the first and second spherical thrust bearings disposed in surrounding relation to said sphere, the first and second spherical thrust bearings being held in the wobble plate such that mutating movement of the wobble plate induces rectilinear translation of the plunger members within respective bores in the cylinder block.
 20. The variable displacement positive displacement pump as in claim 19 and further including a lubricant in the housing member for lubricating mating surfaces of the sphere and the spherical thrust bearings.
 21. A variable displacement positive displacement pump comprising: (a) a housing member; (b) a cylinder block having a plurality of bores equally radially and circumferentially spaced from a central axis of said cylinder block, said cylinder block being affixed to the housing; (c) a plunger member having first and second ends disposed in each of said plurality of bores; (d) a drive shaft journaled for rotation in the housing member along an axis aligned with the central axis of the cylinder block; (e) a swash plate pivotally affixed to the drive shaft and rotatable therewith; (f) a non-rotatable wobble plate assembly having a central bore formed therethrough, with an annular bearing disposed in the bore of the wobble plate in surrounding relation to the swash plate; (g) means for coupling the first end of each of said plunger members to the wobble plate for imparting reciprocating axial displacement to the plunger members when the drive shaft is rotated and the swash plate is at an inclined angle to the drive shaft; (h) a cylinder head member affixed to the cylinder block defining a suction manifold and a discharge manifold, the suction manifold including an inlet port and the discharge manifold having a discharge port; (i) valve assembly for each of the plunger members disposed in the cylinder head and arranged such that a first valve closes to isolate the discharge manifold from the suction manifold during a suction stroke of the plunger member while a second valve opens to allow fluid to flow from the suction manifold into a changing volume of the cylinder bore as the plunger member moves in a direction away from the cylinder head and the first valve opens while the second valve closes as the plunger moves in a direction toward the cylinder head; and (j) means for adjusting the inclined angle of the swash plate and wobble plate relative to the central axis of the cylinder block to vary the stroke of the plunger members with the pump operating.
 22. The variable displacement positive displacement pump of claim 21 wherein the means for adjusting the inclined angle of the swash plate and wobble plate comprises a slide mechanism disposed on the drive shaft to be slidable therealong and rotatable therewith, the slide mechanism being linked to the swash plate for incrementally adjusting a tilt angle between the non-rotatable wobble plate and the axis of the drive shaft.
 23. The variable displacement positive displacement pump as in claim 22 and further including at least one lead screw operatively coupled between the housing and the slide mechanism and a worm gear for rotating the lead screw.
 24. The variable displacement positive displacement pump as in claim 23 wherein the worm gear is driven by a worm shaft, said worm shaft being either manually or automatically rotated.
 25. The variable displacement positive displacement pump as in claim 22 and further including a pair of lead screws operatively coupled between the housing and the slide mechanism and a pair of worm gears for driving the pair of lead screws.
 26. The variable displacement positive displacement pump as in claim 25 and further including a worm shaft having a pair of worms thereon for engaging the pair of worm gears and means for driving the worm shaft.
 27. The variable displacement positive displacement pump as in claim 26 wherein the means for driving the worm shaft is a manually operable crank.
 28. The variable displacement positive displacement pump as in claim 26 wherein the means for driving the worm shaft is a servo motor.
 29. The variable displacement positive displacement pump as in claim 25 herein the slide mechanism comprises a slide on said drive shaft, a control yoke, and a set of bearings disposed between the slide and the control yoke, said control yoke carrying a pair of ball nuts that are in threaded engagement with the pair of lead screws.
 30. The variable displacement positive displacement pump as in claim 21 and further including means supported from the housing and engaged with the wobble plate to prevent rotation of the wobble plate with the swash plate.
 31. The variable displacement positive displacement pump as in claim 21 wherein the valve assembly for each plunger comprises: (a) a valve body having first and second axially displaced, concentric annular valve seat members; (b) a first compression spring for urging the first valve against the first valve seat member; and (c) a second compression spring for urging the second valve against the second valve seat member.
 32. A variable displacement, positive displacement pump comprising: (a) a pump body; (b) a cylinder block affixed to one end of the pump body; (c) a suction manifold affixed to the cylinder block; (d) a discharge manifold affixed to the suction manifold; (e) a drive shaft journaled for rotation in the pump body along a central axis of the pump body, cylinder block, suction manifold and discharge manifold; (f) a swash plate having a tapered aperture therethrough for receiving a portion of the drive shaft therein, the swash plate being pivotably attached to the drive shaft for allowing the swash plate to be tilted at a desired angle to the central axis; (g) a non-rotatable wobble plate assembly journaled with respect to the swash plate by bearings whereby rotation of the drive shaft and swash plate causes the wobble plate assembly to nutate, but not rotate; (h) at least one cylinder bore in the cylinder block extending parallel to and radially offset from the central axis; (i) a plunger member disposed in the cylinder bore and coupled to the wobble plate assembly such that nutating motion of the wobble plate assembly imparts pure reciprocating motion to the plunger member within the cylinder bore; and (j) a valve assembly aligned having first and second poppets longitudinally with the cylinder bore for allowing a liquid entering the suction manifold to be drawn into the cylinder bore during a suction stroke of the plunger member and to be discharged into the discharge manifold during a discharge stroke of the plunger member.
 33. The variable displacement, positive displacement pump of claim 32 and further including means for adjusting the angle that the swash plate is tilted while the drive shaft is being driven.
 34. The variable displacement, positive displacement pump of claim 32 wherein the plunger member is coupled to the wobble plate assembly with a ball joint.
 35. The variable displacement, positive displacement pump as in claim 32 and further including a movable closed spring loaded safety valve disposed between the discharge manifold and the suction manifold that opens when the hydraulic pressure in the discharge manifold reaches a predetermined value.
 36. The variable displacement, positive displacement pump as in claim 32 and further including anti-rotation means operatively coupled between the pump body and the wobble plate assembly that precludes rotational movement of the wobble plate while allowing nutating movement thereof.
 37. The variable displacement, positive displacement pump as in claim 32 and further including a seal assembly disposed in the cylinder bore in surrounding relation to the plunger member. 